1. Field of the Invention
The present invention relates to a substrate holding device holding a substrate by vacuum suction.
2. Description of the Related Art
Generally, in a manufacturing line of a semiconductor wafer or the like, a photolithography technology is used for forming a pattern of resist on a front surface of a substrate such as the semiconductor wafer or an LCD substrate. This photolithography technology can form a predetermined resist pattern on the front surface of the substrate by performing a series of treatments such as a resist coating treatment of applying a resist solution on the front surface of the substrate, exposure treatment of exposing a pattern on the formed resist film, a developing treatment of supplying a developing solution to the substrate after the exposure treatment and so on. As an apparatus performing the series of treatments, a coating and developing apparatus is known. The coating and developing apparatus is a complex apparatus composed of a plurality of process treatment apparatuses performing the treatments, in which a wafer is delivered between the treatment apparatuses by a substrate transfer device and subjected to the series of treatments in a predetermined order. This substrate transfer device includes a transfer arm for holding and transferring the substrate, and a structure in which a suction member for holding the substrate by vacuum suction is attached to the transfer arm is known.
Conventionally, as the substrate for vacuum-sucking the substrate while coping with the warpage, distortion, inclination or the like of the substrate, the following one is known. Specifically, a suction member is attached to freely protrude and retract from/to a base, and the suction member is composed of a lower member and an upper member. The upper member is biased upward by a coil spring, and a suction surface is formed on the surface of the upper surface. Further, a spherical ball part formed on the lower side of the center of the upper member is fitted and connected to a sliding surface in the form of a spherical inner surface formed at the upper portion of the center of the lower member, so that slide of a spherical joint obtained by the connection makes the suction surface freely incline in a swinging manner with respect to the lower member. To maintain the negative pressure in an exhaust path formed in the structure, airtightness of each of center holes of a support shaft portion of the lower member and a pedestal member and annular grooves of a sleeve member and the pedestal member press-inserted into the lower member is maintained by a labyrinth structure fitted thereto. Further, in order to increase the airtightness of the exhaust path, an O-ring is attached in a manner to come into contact with the bottom surface of the lower member so that when the suction member is lowered, the pedestal member and the O-ring are brought into contact with each other (see Patent Document 1).    Patent Document 1: Japanese Laid-open Patent Publication No. H8-229866